1. Field of the Invention
The present invention relates to electrical cables and, in particular, to ribbon cable jumpers of the type used to connect printed circuit boards and other electrical devices.
2. Background of the Invention
Flat or ribbon cables are useful in a variety of applications in which multiple discrete signals must be carried on separate wires in a restricted space. The cables generally consist of a plurality of bare wires laminated between flexible insulating fabric or plastic layers. Such flexible cables are especially suitable as circuit board connectors or jumpers in computers and in telephone switching systems.
However, in conventional ribbon or flat cables, the flexibility of the cable is limited by the size of the individual wires in the cable. The thicker the wires, the greater the stiffness.
In certain applications, for example in the case of jumpers between a circuit board and the flying heads of a magnetic disk drive, it is essential that the stiffness of the jumper not interfere with the ability of the heads to maintain a constant spacing from the disk. In other applications, lack of flexibility may prevent the cable from bending sufficiently to fit into small spaces and tortuous paths. It has often proven impossible to use conventional ribbon cables in such applications.
An additional problem with prior ribbon cables has been the problem of termination. Conventionally, ribbon or flat cables have been connected to circuit boards by using separate specially adapted connectors. The thinner and more flexible the wires in the cable, the more difficult it is to terminate them with a connector. In order to connect the cable to the circuit board the connector must first be connected to the cable. Typically, the circuit boards to which the cables will be connected will have holes provided therein into which the connector can then be plugged.
While ribbon cable connectors generally work well for their intended purpose, the use of discrete connectors is disadvantageous in that it may significantly increase the cost and complexity of the above-mentioned systems. Even the simplest conventional ribbon cable connector requires at a minimum a terminal or pin for each of the wires in the cable, and means for connecting the pins or terminals to the individual wires through, or by removing, the insulation.